ABSTRACT
The use of nitrate/nitrite as electron acceptor during the biological removal of phosphate helps to reduce the carbon requirements and sludge production of wastewater treatment plants. Although simultaneous phosphate (P)-removal and nitrate reduction has been observed in laboratory studies as well as full-scale plants, several studies indicate that both polyphosphate accumulating organism (PAO) I and PAO II are only capable of using nitrite as external electron acceptor. Candidatus Accumulibacter phosphatis are one of the main PAO performing the biological removal of phosphate in wastewater treatment plants (WWTP). The anoxic and aerobic P-uptake capacity, after adaptation to nitrate presence in both cultures was assessed using three electron acceptors: oxygen, nitrate, and nitrite. The PAO I community enriched in this study could take up phosphate efficiently under anoxic conditions using nitrite as electron acceptor. This could be a reason for the regularly observed instabilities observed in enhanced biological phosphorus removal performances of full scale WWTP.
